Add seinfo parsing to PackageManagerService.

This patch set allows the PMS to parse the
mac_permissions.xml file which contains the
seinfo values. Each package that is installed
on the device will be assigned an seinfo value
based on policy. This seinfo value will help label
the app process and data directory. Modifications
also include, adjustments to ApplicationInfo.java
to store the seinfo tag per package, adjustments
to installd to communicate the seinfo tag to
libselinux, and finally a set of unit tests.

Change-Id: I489cfb9cc9cb112d00fbf5e010f9d0d8f6265ade
Signed-off-by: rpcraig <rpcraig@tycho.ncsc.mil>